The present invention relates to the field of tissue repair, specifically, the regeneration of a functional periodontal attachment apparatus destroyed by periodontitis. Specifically, the present invention relates to methods and compositions useful for the repair of periodontal defects, such as lesions involving the alveolar bone, periodontal ligament, and for the regeneration of cementum.
Periodontal disease is a bacterially induced, host mediated, inflammatory disease that results in a loss of connective tissue attachment to the tooth and loss of alveolar bone. It is estimated that upwards of twenty-five percent of the population from 18 to 65 years old has some significant loss of connective tissue support at one or more sites. It is projected that nearly 10% of this population has attachment loss at multiple locations consistent with a diagnosis of moderate periodontitis.
Current periodontal disease therapies are directed at control of the inflammatory disease with the goal of preventing future disease. It is also desirable to seek to regenerate a functional periodontal attachment. To date, autogenous and allogeneic bone grafting has been the method most often used for defect filling and regeneration. However, other reconstructive surgical procedures, using synthetic alloplastic grafts or guided tissue regeneration with physical barriers are also performed.
Autogenous bone grafts are disadvantageous mainly in that they require surgery at a second site in order to obtain sufficient graft material, resulting in patient morbidity. Bone allograft may be obtained from tissue banks either fresh frozen or freeze-dried. Fresh tissue may be antigenic and is subject to limitations of current supply. Freeze-drying markedly reduces antigenicity of bone allograft, but may also decrease the osteogenic potential of the graft as well. Demineralization of the allograft may enhance osteogenic potential, but it decreases the structural integrity of the graft. In addition, the source is human donor bone which creates a risk of transmission of disease.
Alloplastic bone substitutes which have been tried include synthetic or natural hydroxyapatite, which is non-resorbable, beta tricalcium phosphate (resorbable) and polymer of polymethacrylate beads coated with polyhema bovine bone products. These materials tend to be encapsulated with minimal or no bone formation and also may cause root resorption. These bone substitutes may also cause ankylosis, and may not be suitable for regeneration of the cementum and of the periodontal ligament.
Guided tissue regeneration provides a physical barrier between the gum flap and the tooth surface to enhance the potential for wound healing. This procedure retards the apical migration of epithelium, excludes gingival connective tissue from the wound and favors healing from the periodontal ligament space. However, this procedure is technique- and site-sensitive, may leave space between the gum flap and tooth surface and does not reproducibly lead to repair of the periodontal defect.
Accordingly, despite substantial endeavors in this field, there remains a need for an effective method of repair of periodontal defects.
The present invention provides methods and compositions for regenerating periodontal tissue. In a particular embodiment, the present invention comprises methods of treating supraalveolar lesions, which have historically been difficult to treat because they involve both vertical and horizontal lesions of the alveolar bone. The methods and compositions of the present invention are advantageous in that they utilize osteogenic proteins and/or ligament-inducing proteins, which may be produced via recombinant DNA technology, and therefore are of potentially unlimited supply, and are not subject to the same concerns of contaminated source as are bone grafts. The methods and compositions of the present invention are further advantageous in that regeneration is begun of all three tissues comprising the periodontal attachment apparatus: alveolar bone, periodontal ligament space and cementum; which minimizes the occurrence of potentially undesirable conditions such as ankylosis and root resorption.
According to the present invention, methods and compositions are provided for treatment of periodontal disease and for repair of periodontal lesions to the alveolar bone, particularly supraalveolar lesions which involve both vertical and horizontal lesions of the alveolar bone. Supraalveolar defects may affect areas in which the teet remain intact, in which case it is desirable to regenerate the entire periodontal attachment apparatus between alveolar bone and tooth. Alternatively, supraalveolar defects may affect areas in which the teeth have been lost, in which case it is desirable to augment the alveolar bone in order to allow more effective implantation of substitute teeth. In addition to supraalveolar defects, the methods and compositions of the present invention are useful for the treatment of mandibular and maxillary class II and III furcation and interproximal defects with and without bacterial involvement from periodontitis, as well as for ridge augmentation of both the mandibular and maxillary structures. Class II and III furcations and interproximal defects are subclasses of supraalveolar defects in which the teeth remain present. Ridge augmentation is often necessary when a patient has experienced substantial resorption of the mandibular and/or maxillary structures. This often occurs in patients who have been missing one or more teeth for an extended period of time.
The methods comprise applying to the site of a supraalveolar lesion, or to the site of a class II or class III furcation or interproximal defect, or to the mandibular or maxillary ridge requiring augmentation, an amount of a composition comprising one or more purified osteogenic and/or ligament-inducing proteins, which is effective to regenerate the alveolar mandibular and/or maxillary bone in both a vertical and horizontal direction. The methods and compositions are advantageous in that regeneration of the mandibular and/or maxillary bone in both a vertical and horizontal direction often results in bone which is better able to support dental implants. The methods and composition are further advantageous in that repair or improvement may be obtained of the entire periodontal attachment apparatus: the alveolar bone, the periodontal ligament space and the cementum layer. The method may further comprise the administration of a composition comprising a purified osteogenic and/or ligament-inducing protein to a site of periodontal lesion or defect in a suitable carrier such that the alveolar bone, the periodontal ligament apparatus, and the cementum layer are regenerated, without significant ankylosis and/or root resorption appearing. The composition is preferably administered in combination with an effective carrier. One of the key advantages of the method of the present invention is that it allows for the controlled regeneration of alveolar bone, periodontal ligament and cementum tissue in a manner which minimizes the occurrences of undesirable ankylosis and root resorption.
The osteogenic protein is preferably from the subclass of proteins known generally as bone morphogenetic proteins (BMP), which have been disclosed to have osteogenic activity. These BMPs include BMP-2, BMP-4, BMP-5, BMP-6, BMP-7, BMP-8, BMP-9, BMP-10 and BMP-11 and may also include other members of the TGF-,xcex2 superfamily of proteins. The structures of a number of BMP proteins are disclosed in U.S. Pat. Nos. 4,877,864; 5,108,922; 5,013,649; 5,116,738; 5,106,748; 5,187,076; 5,141,905; and in PCT applications WO 91/18098; WO 93/00432; W094/26893; and W094/26892, the disclosures of which are hereby incorporated by reference. The preferred osteogenic protein is BMP-2, the sequence of which is disclosed in U.S. Pat. No. 5,013,649, the disclosure of which is hereby incorporated by reference. Other BMPs known in the art can also be used. The ligament-inducing protein is preferably also from the BMP subclass of the TGF-3 superfamily of proteins, but which have been disclosed to have tendon/ligament-like tissue inducing activity. These proteins include BMP-12, BMP-13 and MP52, and may also include other members of the TGF-xcex2 superfamily of proteins. These proteins and their activity are described in U.S. patent application, Ser. No. 08/217,780, filed on Mar. 25, 1994, 08/333,576, filed on Nov. 2, 1994, and 08/362,670, filed on Dec. 22, 1994, the disclosures of which are hereby incorporated by reference. Presently, the most preferred osteogenic protein is BMP-2, and the most preferred ligament-inducing protein is BMP-12. In a preferred embodiment, both one or more osteogenic proteins and one or more ligament-inducing proteins as described above are used. The most preferred combination of osteogenic and ligament-inducing proteins is BMP-2 and BMP-12. The BMPs may be recombinantly produced, or purified from a protein composition. The BMPs may be homodimeric, or may be heterodimeric with other BMPs (e.g., a heterodimer composed of one monomer each of BMP-2 and BMP-6) or with other members of the TGF-xcex2 superfamily, such as activins, inhibins and TGF-xcex21 (e.g., a heterodimer composed of one monomer each of a BMP and a related member of the TGF-xcex2 superfamily). Examples of such heterodimeric proteins are described for example in Published PCT Pat. Application WO93/09229, the specification of which is hereby incorporated herein by reference. In a preferred embodiment, the protein is a heterodimer of an osteogenic BMP, such as BMP-2, and a ligament-inducing BMP, such as BMP-12. The amount of osteogenic protein useful herein is that amount effective to stimulate increased osteogenic activity of infiltrating progenitor cells, and will depend upon the size and nature of defect being treated, as well as the carrier being employed. Similarly, the amount of ligament-inducing protein useful herein is that amount effective to stimulate increased ligament-forming activity of progenitor cells, and will depend upon the size and nature of the defect, as well as the carrier. Generally, the amount of either protein to be delivered is in a range of from about 0.05 to about 1.5 mg per cc or ml of carrier. In the embodiment wherein both an osteogenic protein and a ligament-inducing protein are employed, the proteins are preferably employed in a ratio of from about 90:10 to 10:90 percent osteogenic protein:ligament-inducing protein; most preferably in a ratio from about 60:40 to about 40:60.
Materials which may be useful as the carrier in practicing the present invention include pharmaceutically acceptable materials having viscosity and polarity such that, when added to the bone morphogenetic protein, form a composition that possesses appropriate handling characteristics (i.e., is neither too runny to remain at the defect or lesion site nor too firm so as not to be moldable) for application to the site of periodontal disease or lesion. Adding the carrier to the bone morphogenetic protein allows the protein to remain in the disease or lesion site for a time sufficient to allow the protein to increase the otherwise natural rate of regenerative osteogenic activity of the infiltrating mammalian progenitor cells, and to form a space in which new tissue can grow and to allow ingrowth of cells. The carrier may also allow the bone morphogenetic protein to be released from the lesion, defect or disease site over a time interval appropriate for optimally increasing the rate of regenerative osteogenic and ligament-forming activity of the progenitor cells.
A preferred family of carriers for administration of the bone morphogenetic proteins are porous particulate polymers, described in detail in U.S. Pat. No. 5,171,579, the entire disclosure of which is incorporated herein by reference. The protein and polymers are preferably sequestered by a sequestering agent, such as autologous blood. An alternative carrier useful for the present invention is a formulation of osteogenic protein, porous particulate polymers and another sequestering agent, such as cellulosic material. Other preferred sequestering agents include hyaluronic acid, sodium alginate, poly(ethylene glycol), polyoxyethylene oxide, carboxyvinyl polymer and poly(vinyl alcohol). Most preferred as the sequestering agent for this embodiment is carboxymethylcellulose. These compositions are described in the published PCT application WO 93/00050, the entire disclosure of which is hereby incorporated herein by reference. The cellulosic protein sequestering agent is preferably present in a concentration of about 1 to about 10% (w/v implant). The porous particulate polymer/cellulosic sequestering agent may optionally be further combined with aqueous glycerol as a diluent, preferably in concentrations of about 10 to about 80% (v/v); and ratios of sequestering agent/liquid solution:porous particulate polymers are preferably from about 0.1 to about 0.9 (v/v). The amount of osteogenic and/or ligament-inducing protein used with porous particulate polymers is generally in the range of 0.01 to 1 mg of protein, preferably 0.05 to 0.6 mg protein for each cubic centimeter of composition employed.
Another preferred family of carriers is collagenous materials. Suitable collagen materials include Collastat(copyright) and Helistat(copyright) collagen sponges (Integra LifeSciences Corp., Plainsboro, N.J.). Other collagen materials which may be suitable for use in the present invention are described in U.S. Pat. Nos. 5,206,028; U.S. Pat. No. 5,024,841; U.S. Pat. No. 5,256,418. The collagen carrier is preferably in the form of a sponge. The collagen sponge may be loaded with protein prior to administration by soaking the sponge in the desired volume and concentration of protein for a suitable time period. The collagen sponge is preferably soak loaded with protein in a range from about 10% to about 150% v/v [ml protein/cc dry sponge], more preferably about 10 to about 60% v/v. Alternatively, the protein may be adsorbed to the collagen sponge during production. In this case, bone morphogenetic protein is preferably added to the collagen sponge during production and lyophilized to form a unitary product. The protein is preferably added in a ratio of from about 10 to about 150% v/v, more preferably in a range from about 60 to about 80% v/v.
Another preferred family of carriers is cellulosic materials such as alkylcellulose (including hydroxyalkylcellulose), including methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropyl-methylcellulose, and carboxymethylcellulose, the most preferred being the cationic salts of carboxymethylcellulose (CMC).
In the case of cellulosic carriers, it is preferred that the carrier be in the form of a hydrated cellulosic viscous gel. Viscosity of cellulosic materials may be increased through mechanical means, such as high agitation for a suitable period of time, followed by autoclaving. The bone morphogenetic protein and cellulosic carrier is in a solution of suitable buffer. One preferred buffer solution is a composition comprising, in addition to the osteogenic and/or ligament-inducing protein, about 1.0 to about 10.0% (w/v) glycine, about 0.1 to about 5.0% (w/v) of a sugar, preferably sucrose, about 1 to about 20 mM glutamic acid hydrochloride, and optionally about 0.01 to about 0.1% of a non-ionic surfactant, such as polysorbate 80. Preferred solutions are from about 1% to about 20% w/v cellulosic carrier/buffer. If desired, a salt may be added. A preferred viscous gel carrier is described in Example 2 below. The amount of osteogenic and/or ligament-inducing protein useful with viscous gel carrier is generally in a range of from about 0.05 to about 1.5 mg, preferably from about 0.1 to about 1.0 mg per cubic centimeter of implant material required.
Other materials which may be suitable for use as carriers for bone morphogenetic proteins in the methods and compositions of the present invention include demineralized bone, and minerals and ceramics, such as calcium phosphates, hydroxyapatite, etc. Other potential carriers include carriers for injectable formulations of BMPs. Suitable carriers for injectable formulations include, for example, soluble collagen, hyalouronic acid, polylactic acid/polyethylene glycol, and polymers.